The present invention relates to a forehead support for a facial mask used to supply breathable gas to a wearer""s airways.
The invention has been developed primarily for use in supporting a nasal mask used in Continuous Positive Airway Pressure (CPAP) treatment of, for example, Obstructive Sleep Apnea (OSA) and other ventilatory assistance treatments such as Non-Invasive Positive Pressure Ventilation (NIPPV) and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to these particular uses and is also suitable for use with, for example, full-face (ie. nose and mouth) masks.
CPAP treatment is a common emeliorative treatment for breathing disorders including OSA. CPAP treatment, as described in U.S. Pat. No. 4,944,310, provides pressurised air or other breathable gas to the entrance of a patient""s airways at a pressure elevated above atmospheric pressure, typically in the range 4-20 cm H2O.
It is also known for the level of treatment pressure to vary during a period of treatment in accordance with patient need, that form of CPAP being known as automatically adjusting nasal CPAP treatment, as described in U.S. Pat. No. 5,245,995.
NIPPV is another form of treatment for breathing disorders which can involve a relatively higher pressure of gas being provided in the patient mask during the inspiratory phase of respiration and a relatively lower pressure or atmospheric pressure being provided in the patient mask during the expiratory phase of respiration.
In other NIPPV modes the pressure can be made to vary in a complex manner throughout the respiratory cycle. For example, the pressure at the mask during inspiration or expiration can be varied through the period of treatment.
Typically, the ventilatory assistance for CPAP or NIPPV treatment is delivered to the patient by way of a nasal mask. Alternatively, a mouth mask or full face mask or nasal prongs can be used. In this specification any reference to a mask is to be understood as incorporating a reference to a nasal mask, mouth mask, full face mask or nasal prongs.
In this specification any reference to CPAP treatment is to be understood as embracing all of the above described forms of ventilatory treatment or assistance.
A CPAP apparatus broadly comprises a flow generator constituted by a continuous source of air or other breathable gas such as a hospital piped supply or a blower. In the latter case, an electric motor drives the blower and is typically controlled by a servo-controller under the control of a microcontroller unit. In either case, the gas supply is connected to a conduit or tube which in turn is connected to a patient nasal or full-face mask which incorporates, or has in close proximity, an exhaust to atmosphere for venting exhaled gases. Examples of prior art nasal masks are shown in U.S. Pat. Nos. 4,782,832 and 5,243,971.
The supply conduit delivers gas into a chamber formed by walls of the mask. The mask is normally secured to the wearer""s head by straps. The straps are adjusted to pull the mask against the face with sufficient force to achieve a gas tight seal between the mask and the wearer""s face.
A problem that arises with the use of the existing masks is that in order for the straps to be tight, the mask is compressed against the wearer""s face and may push unduly hard on the wearer""s nose. Additionally, the mask may move around the wearer""s face. Thus, there has been hitherto provided a forehead support, which provides a support mechanism between the mask and the forehead. This forehead support prevents both the mask from pushing too strongly against the wearer""s nose and/or facial region as well as minimising movement of the mask with the addition of a contact point between the mask and the wearer""s head thereby reducing uncomfortable pressure points. Additionally, the forehead support can be arranged to prevent the gas supply conduit from contacting the wearer""s forehead or face.
Forehead supports with a single cushion and a single contact point or the forehead are known.
The applicant""s U.S. patent application Ser. No. 09/008,708 relates to a substantially rigid one-piece forehead support having a pair of forehead cushions mounted at each outer end of the support. This forehead support is connected to the top of a facial mask and includes an adjustable mechanism to allow the spacing between the top of the facial mask and the forehead support to be altered between predetermined positions to thereby alter the angle of the mask relative to the wearer""s head to suit the wearer""s facial topography.
It is an object of the present invention to provide an alternate form of forehead support.
Accordingly, in a first aspect, the present invention provides a forehead support for a respiratory mask, said forehead support including a pair of arms, wherein: the arms are each adapted to locate a forehead cushion; the arms are adapted to pivot relative to each other; and the arms are selectively lockable at two or more angular positions relative to each other.
In a second aspect, the present invention provides a respiratory mask assembly comprising a respiratory mask and a forehead support, said forehead support including a pair of arms, wherein: the arms are each adapted to locate a forehead cushion; the arms are adapted to pivot relative to each other; and the arms are selectively lockable at two or more angular positions relative to each other.
As the angle between the arms adjacent to wearer""s forehead is decreased or increased the distance between the forehead and the extension of the respiratory mask is increased or decreased respectively, thereby altering the angle of the respiratory mask relative to the wearer""s face.
The arms are preferably also adapted to each pivot relative to the respiratory mask.
Preferably, each of the arms include a cylindrical recess adapted to pivotally receive a cylindrical boss provided on the respiratory mask.
The respiratory mask preferably includes an extension adjacent and above, in use, the wearer""s nose on which the cylindrical boss is provided.
Desirably, one of the arms includes a tongue adapted to be received in one of at least two grooves provided on the other of the arms so as to lock the arms at one of two or more predetermined said angular positions.
The tongue is preferably provided on a flexible member which is adapted to permit the tongue be moved out of engagement with the grooves by manual manipulation of the member.
The forehead cushions are desirably located on the outer ends of the arms.
The arms preferably also include means to connect a head strap thereto.
The respiratory mask preferably also includes means to connect a head strap thereto.